Selective sync is a desktop app feature that lets you choose which folders sync from your Dropbox account to the Dropbox folder on your computer. With selective sync you can save space on your hard drive while still ensuring all your files are safely backed up to dropbox.com.

Wait until a folder has completely uploaded (displaying a green checkmark) before unchecking it in your selective sync settings

If you use Linux and have the Dropbox command line instructions script, you can add a folder to the "do not sync" list in Terminal: "/path/to/dropbox.py exclude add ~/Dropbox/path/to/folder/" (simply substitute "/path/to/" with the actual paths to the CLI script and the folder or file, respectively)

Selective sync and shared folders

Unchecking a shared folder will stop that folder from syncing to your computer. However, you’ll still be a member of that shared folder, and it will still appear in your account on dropbox.com. The shared folder will also remain active for other members of that folder. To remove yourself from a shared folder, you can either leave the shared folder from dropbox.com or, if you're the owner of a shared folder, you can unshare it.

Team selective sync

If you’re on a Dropbox Business team, your admin may also have turned on team selective sync. This feature allows team admins to create a default selective sync setting for a team folder (or a folder in the team space). This default then applies for all new members of a Dropbox Business team with access to that folder.

Smart Sync

If you have a Dropbox Business or Professional account, you can also use Smart Sync to manage hard drive space on your computer. Smart Sync allows you to see all of the files in your Dropbox on your computer, but only downloads the ones that you want. You can use both Smart Sync and selective sync together, or choose just one.

Troubleshoot issues with selective sync

How fast can selective sync free up space on my hard drive?

Usually, selectively syncing files will free up space on your hard drive within minutes (as long as your computer is online and able to sync to Dropbox). However, there is a known limitation with macOS 10.13 (High Sierra):

Apple's operating system macOS 10.13 (High Sierra) uses a new type of file system called APFS. With APFS, the operating system takes snapshots of the file system and available hard drive space. These snapshots may not update after you've selectively synced Dropbox files. This means that hard drive space you freed up with selective sync may not be immediately reflected or available if this snapshot hasn't updated.

This hard drive space should eventually be freed up by the OS, but the amount of time this will take can vary. This isn't a behavior specific to Dropbox, but instead the designed behavior of macOS.